1. Field of the Invention
The present invention relates to a still image signal recording apparatus and, more particularly, to a still image signal recording apparatus capable of recording an image of a high degree of fineness.
2. Description of the Prior Art
In recent years, video signal recording and reproducing apparatuses which make use of a magnetic tapes of 8 mm width, generally referred to as 8 mm VTRs, are becoming popular. Referring to the FIG. 1, a reference numeral 1 denotes a magnetic tape, 2 denotes a track in which video signals are recorded, and 3 denotes a track in which PCM audio signals are recorded. The tracks 2 and 3 are aligned in the direction of lengths thereof.
The present applicant has proposed, in the specification of U.S. patent application Ser. No. 937,872, to use the tracks 3 storing PCM audio signals also for the purpose of recording digital still image signals. Assuming that the resolution of the still image is greater than that of the moving image, it is possible to utilize the 8 mm VTR for the purpose of recording still images.
A description will be made hereinunder as to the manner in which still image data is recorded in the magnetic tape 1. In general, the record data rate of a PCM audio signal in 8 mm VTRs has to be at least 630 Kbit/sec (2f.sub.H .times.2.times.10 .apprxeq.630Kbit/sec) on the basis of so-called user rate, where 2f.sub.H represents the frequency of sampling of the audio signal.
It is assumed here that an NTSC signal, each frame of which including a luminance signal and a color difference signal, is sampled at a frequency of 4f.sub.sc (f.sub.sc represents the color subcarrier frequency). In such a case, the amount of data to be carried by each frame is represented by 4.sub.fs .times.8.times.1/30.apprxeq.3.8Mbit/frame. Therefore, the recording of a still image at the recording rate of PCM audio signal takes about 6 seconds. Several tens of seconds will be required for recording a high definition television signal (HDTV).
The recording of a still image at the recording rate of PCM audio signal requires a very large number of tracks. If the recording is started from a random position, the number of still images which are recorded incompletely will be increased.